Four billion dollars, that's what BP has agreed to pay to resolve criminal charges connected to the 2010 spill in the Gulf of Mexico. It is the largest criminal penalty in history. On top of that, a more than $500 million fine from the Securities and Exchange Commission. In New Orleans today, BP pleaded guilty to charges including felony manslaughter for the 11 men who perished on the Deepwater Horizon rig and obstructing a congressional investigation. NPR's Carrie Johnson begins our coverage.

CARRIE JOHNSON, BYLINE: Two years ago, Attorney General Eric Holder traveled to New Orleans and promised he would deliver justice for the oil spill that devastated the Gulf. Today, Holder returned with a settlement in hand.

ATTORNEY GENERAL ERIC HOLDER: This marks both the largest single criminal fine - more than $1.25 billion - and the largest total criminal resolution - $4 billion - in the history of the United States.

JOHNSON: BP admitted to 14 criminal charges, felonies related to the deaths of 11 men on board the rig the night it exploded, violations of key environmental laws such as the Clean Water Act and the Migratory Bird Act, and another count of lying to Congress about how much oil was flowing into the Gulf after disaster struck. On Capitol Hill, Massachusetts Democrat Ed Markey, a member of the U.S. House, had this to say.

REPRESENTATIVE ED MARKEY: BP lied to me. They lied to the people of the Gulf, and they lied to their shareholders, and they lied to all Americans.

JOHNSON: Lanny Breuer leads the criminal division at the Justice Department. He blamed a culture of negligence within BP.

LANNY BREUER: The explosion of the rig was a disaster that resulted from BP's culture of privileging profit over prudence.

JOHNSON: BP chief executive Bob Dudley apologized for its role in the accident and said the company had accepted responsibility. Under the terms of the plea deal, BP also agreed to open its deepwater drilling practices to an independent monitor. The company will also serve a form of corporate probation for five years. David Uhlmann is a law professor at the University of Michigan.

DAVID UHLMANN: You can't put the corporation in jail. So the government's always going to be limited, in a corporate prosecution, to fines, probation.

JOHNSON: BP has been in trouble before for disasters in Alaska and Texas, where it shelled out money and promised to change. The consumer group Public Citizen blasted today's deal as a slap on the wrist. Reporters in New Orleans asked the attorney general the same thing.

HOLDER: The company has pled guilty to criminal felony charges, manslaughter. Individuals have been charged as well. Everything that we are capable of doing in the criminal sphere, we have done today.

JOHNSON: And in a federal court in New Orleans today, prosecutors on the special task force unveiled a 23-count indictment. They charged Donald Vidrine and Robert Kaluza, the two top BP managers onboard the rig, with manslaughter and environmental crimes. Defense lawyers told NPR the men had spent their lives in the oil patch. They said the managers are dedicated and innocent. The Justice Department also charged David Rainey, BP's former head of exploration in the Gulf, with obstruction of justice. Prosecutors say he hid information about the amount of oil gushing out of the well. Rainey's lawyers say they'll fight those charges in court. Today's action is far from the last word on the spill. Holder:

HOLDER: Today's resolution does not, does not mark the end of our efforts. In fact our criminal investigation remains ongoing.

JOHNSON: So is a huge civil trial meant to determine how many billions of dollars BP must pay the Gulf states. A source told NPR the deal was on track with both the federal government and several states on board, until Louisiana threw a wrench in the works over how much money it would get in economic damages. And the financial stakes in those civil cases could top $20 billion. Carrie Johnson, NPR News, Washington. Transcript provided by NPR, Copyright National Public Radio.